1. Field of Invention
The present invention relates to a method and a system of determining failure of a urea quality sensor and, more particularly, to the method and a system of determining the failure of the urea quality sensor that indicates the failure of the urea quality sensor to a driver and operates compulsory inducement if a urea quality is bad.
2. Description of Related Art
Generally, an exhaust gas exhausted through an exhaust manifold from an engine is led to a catalytic converter formed on an exhaust pipe and is purified. After that, noise of the exhaust gas is reduced during passing through a muffler and is exhausted to the air through a tail pipe.
A selective catalytic reduction (SCR) converter is one type of such catalytic converters. The SCR means that reducing agents such as urea, ammonia, carbon monoxide and hydrocarbon (HC) react better with nitrogen oxide than oxygen.
An exhaust system of a vehicle provided with the SCR converter includes a urea tank and a dosing module. The dosing module injects the reducing agents such as the urea into the exhaust gas passing through the exhaust pipe. Thereby, the SCR converter can reduce the nitrogen oxide efficiently.
However, purifying efficiency of the nitrogen oxide in the SCR converter is greatly affected by urea quality. That is, if the urea quality is not suitable, the SCR converter is hard to purify the nitrogen oxide. Therefore, regulations demand that means for warning unsuitable urea quality should be mounted at the vehicle.
Urea quality sensors are increasingly used for warning the unsuitable urea quality. In order to use the urea quality sensor, however, a method of determining failure of the urea quality sensor should be also used.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.